The present invention, in some embodiments thereof, relates to aptamers, multimeric aptamers and uses thereof.
The ErbB family of receptor tyrosine kinases plays an important role in epitheliogenesis, and accordingly serves as a major therapeutic target in several cancers. The family comprises four transmembrane receptors and eleven ligands that induce homo- or heterodimerization upon binding to the respective receptor. ErbB-1 (also called the epidermal growth factor receptor; EGFR) and ErbB-4 share some ligands, whereas no similar ligand is so far known for ErbB-2. Overexpression and mutations of ErbB family members lead to a multitude of malignancies. To date, synthetic tyrosine kinase inhibitors (e.g., Erlotinib and Gefitinib), as well as monoclonal antibodies (mAbs; e.g., Cetuximab and Trastuzumab), have been developed to inhibit pathological signalling, or recruit the immune system to cancer cells. Aptamers might represent an alternative therapeutic modality. These are small, single-stranded DNA or RNA molecules. Aptamers are selected in an evolutionary process called SELEX (Systematic Evolution of Ligands by Exponential Enrichment). A DNA- or RNA-library containing single-stranded random sequences, flanked by two primer-binding regions, is allowed to bind to a specific target. In several selection rounds, binders are amplified and non-specific binders are removed in a partitioning step. Selected sequences can be modified after selection, to improve their stability in different chemical environments (e.g., serum). Different therapeutic aptamers, which are antiviral, anti-coagulation, anti-inflammatory or antiangiogenic, are already in clinical trials. The first clinically approved aptamer is an RNA-molecule, called Macugen, which effectively inhibits macular degeneration. In addition to pharmacological applications, aptamers can be exploited for transducing a binding event into a signal. As a consequence, aptamers have been adapted to a variety of bio-analytical methods.
Several anti-cancer aptamers have been developed, including an aptamer against Nucleolin, which led to phase 2 clinical trials. So far, several anti-ErbB-specific aptamers have been developed [Li N, Nguyen H H, Byrom M, & Ellington A D (2011) Inhibition of Cell Proliferation by an Anti-EGFR Aptamer. PloS one 6(6):e20299; Dastjerdi K, Tabar G H, Dehghani H, & Haghparast A (2011) Generation of an enriched pool of DNA aptamers for an HER2-overexpressing cell line selected by Cell SELEX. Biotechnology and applied biochemistry 58(4):226-230; Esposito C L, et al. (2011) A neutralizing RNA aptamer against EGFR causes selective apoptotic cell death. PloS one 6(9):e24071; Kim M Y & Jeong S (2011) In vitro selection of RNA aptamer and specific targeting of ErbB2 in breast cancer cells. Nucleic acid therapeutics 21(3):173-178; Chen C H, Chernis G A, Hoang V Q, & Landgraf R (2003) Inhibition of heregulin signaling by an aptamer that preferentially binds to the oligomeric form of human epidermal growth factor receptor-3. Proceedings of the National Academy of Sciences of the United States of America 100(16):9226-9231].
These aptamers generally show high affinity and specificity to their targets, and in the case of ErbB-1- and ErbB-3-specific aptamers, they also inhibit the proliferation of cultured cancer cells (Esposito et al. 2011, supra). Notably, an aptamer against ErbB-1/EGFR was able to inhibit tumor growth in a mouse model (Esposito et al. 2011 supra), and ErbB-2-specific aptamers were used to deliver siRNAs targeting Bcl-2 [Dassie J P, et al. (2009) Systemic administration of optimized aptamer-siRNA chimeras promotes regression of PSMA-expressing tumors. Nature biotechnology 27(9):839-849].
Additional background art includes:
U.S. Patent Application Number 20110275702 teaches a ligand-nucleic acid nanostructure that promotes cell-cell interaction. Specially, the ligand-nucleic acid nanostructure is a multimeric aptamer.
U.S. Patent Application Number 20120225088 teaches multimeric aptamers and methods of use.
U.S. Patent Application Number 20120190732 teaches a first ligand that is specific for binding to a tumor cell, and a second ligand that is specific for binding to a death receptor on the tumor cell, wherein the first and second ligands are bound to a nucleic acid nanostructure, wherein the first and second ligands are aptamers.